French Patent No. 2,426,548 discloses a device for interchangeably attaching tools to an industrial robot, wherein a pot-shaped nut is provided on the rotatable end member of the robot. The nut is arranged to be screwed on a stationary threaded portion of the tool by means of the drive of the end member. At their peripheries, the threads of the nut and of the threaded portion are provided with longitudinal grooves. Thus the nut can be pushed axially over the threaded portion, the recesses of the nut extending over the remaining lands of the thread and vice versa. Then the nut is tightened on the threaded portion by rotation of the end member. The tool is supported on a resiliently retained tool support. A central centering pin having a frustro-conical, tapering end is provided on the threaded portion. The centering pin extends into a hub-like central portion of the nut. This central portion has a central bore therein which flares at its end facing the threaded portion.
European patent No. 0,120,275 discloses a tool carrier for engaging tools in industrial robots, wherein a cone is provided on the tool and a conical internal surface complementary thereto is provided on the robot arm. A central locking device serves to pull the cone against the conical inner surface.
The locking device comprises a central pin provided on the cone, this pin carrying a double conical head. A "double-acting jack" comprises a sleeve which slides in a stepped axial bore communicating with the conical inner surface. Balls are located in transverse bores of the sleeve. The sleeve is arranged to be shifted by a piston of the jack. This piston is arranged to be exposed to a control fluid pressure against the action of a spring. In a "lower" position of the piston, which the piston assumes, when it is exposed to the control fluid pressure, the balls are able to yield towards the larger diameter internal surface of the stepped bore. The pin with its double-conical head can be pushed into the sleeve. Thereby the balls are urged radially outwards. When the control fluid pressure is removed, the sleeve will move back under the action of the spring. Thereby the balls will be pushed inwardly by the inner wall of the narrower portion of the stepped bore and will lock the double-conical head. The cone of the tool is then pulled against the conical inner surface of the robot arm by the spring through the balls and the head.